A light source device of a projector using a laser beam source has been proposed. The laser beam source having relatively high output and producing multiple color lights has been developed as a light source of a projector. The laser beam source may includes advantages such as high color reproducibility, immediate lighting, and long life when compared with a UHP lamp used as a light source in a projector. Examples of laser beam sources currently known in the industry involve a type which emits fundamental wave light from the light source without wavelength change, and a type which converts the wavelength of fundamental wave light before emission. The wavelength converting element known for converting the wavelength of the fundamental wave light is, for example, a second-harmonic generation (SHG) element. When the SHG element is employed, a sufficient amount of laser beams having desired wavelength are supplied by using a general-purpose light source easily available. JP-A-6-289446 refers to a technology for a wavelength converting element for obtaining a stable amount of higher harmonic light with high efficiency, for example. The technology proposed in this document produces a temperature difference between the light entering surface of a non-linear optical crystal and the light emitting surface thereof.
It is known in the industry that the phase matching condition of the SHG element collapses when the refractive index distribution changes due to temperature variations. As such, the wavelength conversion efficiency lowers. When the non-linear optical crystal has temperature slope, a part having collapse of phase matching condition appears within the non-linear optical crystal. This part having collapse of phase matching condition lowers the wavelength conversion efficiency of the wavelength converting element. Accordingly, achieving high wavelength conversion efficiency is difficult in such existing technology configurations.